| Cellulose based super absorbent polymer is a novel and green absorbent material made from cellulose.Nowadays,super absorbent polymer is widely used in personal hygiene products,and have a great prospect in the medicine,environmental protection,construction and intelligent components and other fields.In this paper,bamboo shavings and hydroxyethyl cellulose(HEC)were used as cellulose sources to prepared two kinds of super absorbent polymer by aqueous solution polymerization with acrylic acid(AA),acrylamide(AM)and 2-acrylamida-2-methyl-propanesulfonic acid(AMPS).The water absorbency,water retention,degradability and dye adsorption properties were investigated.Main research contents and results are as follows:1.The modified bamboo shavings(MBS)were obtained by pretreated with the solution of H2O2/H2SO4.MBS-co-p(AA-AMPS)/PVA semi-interpenetrating super absorbent polymer was prepared by aqueous solution polymerization with modified bamboo shavings,acrylic acid and 2-acrylamida-2-methyl-propanesulfonic acid,potassium persulfate(KPS)as the initiator,N,N-methylene-diacrylamide(MBA)as the crosslinking agent,and polyvinyl alcohol(PVA)as the additive.The influence of material ratio and reaction conditions on absorbency was investigated.The optimal reaction conditions were as follow:m(MBS):m(AA):m(AMPS):m(PVA):m(KPS):m(MBA)=1.5:6:3:0.1:033:0.012,the neutralization degree of AA was 65%,and the reaction temperature was 75 ?,The absorbency of deionized water and normal saline is 1875.3g·g-1 and 97.1g·-'1 respectively under the optimal conditions.The polymer was characterized by FT-IR,XRD,SEM and TG.The FT-IR results showed that MBS-co-p(AA-AMPS)/PVA semi-interpenetrating superabsorbent polymer was successfully synthesized.The SEM results showed that modified bamboo shavings is beneficial to the grafting reaction because it was etched by H2O2/H2SO4 solution,and the MBS-co-p(AA-AMPS)/PVA semi-interpenetrating superabsorbent has porous structure.The TG results showed that the polymer with excellent thermal stability.The pH sensitivity,water retention,degradability,reusability and the kinetic of the polymer swelling in deionized water were investigated.The water absorbency of the super absorbent polymer was highest when pH was 6,and decreased obviously under the condition of strong acidity and alkalinity.The water retention ratio was still 97.5%after centrifugation with speed of 10000r·min-1 for 30min.The degradation ratio of polymer was 28.0%after soil burial for 45 days.The water absorbency of the polymer was still 83.6%of the first time after recycling for 5 times.The swelling process of the polymer in deionized water fits to the pseudo-second-order kinetics.2.HEC-co-p(AA-AM)/TA super absorbent polymer was prepared by aqueous solution polymerization with hydroxyethyl cellulose,acrylic acid and acrylamide,potassium persulfate as initiator,N,N-methylene diacrylamide as crosslinking agent,tannic acid(TA)as modifying agent.The conditions of the reaction were optimized by single factor experiment and orthogonal experiment,and the optimal reaction conditions were as follow:75?,0.5 g HEC,0.3 g TA,10.0 g AA,2.0 g AM,65%AA neutralization,0.04 g KPS,0.008 g MBA.The absorbency of deionized water was 1180.6g·g'1 under the optimal conditions.FT-IR,SEM and TG were used to characterize the polymer.FT-IR analysis showed that tannic acid was successfully fixed in the polymer and formed hydrogen bonds with carboxyl and amine groups in the polymerization chain.SEM analysis showed that the polymer possesses porous structure by adding tannic acid,and the polymer has uniform pore structure when the amount of tannic acid was 0.3 g.TG analysis showed that the thermal stability of the polymer was enhanced by adding tannic acid.The water retention rate at high temperature,absorbability in different saline solutions,soil evaporation rate,reusability and the kinetic of the polymer swelling in the normal saline were investigated.The polymer has good water retention at high temperature,and the water retention ratio was 28.6%after dehydration for 6 hours at 80?.The polymer was sensitive to salt solution,and its absorbency in different salt solutions was decrease with the increase of ion valence:Na+>Ca2+>Fe3+.The soil with the polymer can significantly reduced the evaporation ratio.When the addition amount of polymer was 1%,the evaporation ratio of the soil was only 71.3%after the soil was placed under natural conditions for 100h.The polymer has excellent recycling performance,and the water absorption ratio was still 85.9%of the first water absorption ratio after 5 times of recycling.The diffusion behavior of normal saline in the polymer fits to the Fickian diffusion and the swelling behavior of the polymer fits to pseudo-second-order kinetics.3.HEC-co-p(AA-AM)/TA super absorbent polymer was used to adsorb methylene blue.The optimum tannic acid content of the polymer was 0.3 g,and the optimum adsorption conditions were as follows:the adsorption temperature is 25?,solid-liquid ratio is 0.2 g·L-1,initial concentration of 800 mg·L-1 MB,pH is 8,the contact time of 120 min.The adsorption capacity of MB on HEC-co-p(AA-AM)/TA super absorbent polymer was 3567.5 mg·g-1 under the optimum condition.The adsorption kinetics,the adsorption isotherm model and the thermodynamics of the adsorption of MB on HEC-co-p(AA-AM)/TA super absorbent polymer was investigated,the results showed that the adsorption reaction is spontaneous,exothermic,entropy reduction.The adsorption process fits to the pseudo-second-order kinetics model and the results of intra-particle diffusion model indicate that intra-particle diffusion is not the only rate-control step in the adsorption process.The adsorption process was fit to Langmuir isotherm model,it means that the adsorption process is belong to the monolayer adsorption.The influence of ion strength on the adsorption and reusability were investigated,the results showed that the polymer has excellent reusability,and the adsorption performance was still 90.4%of the initial adsorption performance after 5 cycles.Finally,the adsorption mechanism was investigated by FT-IR,SEM and XPS.The results showed that MB molecules were reacted with the hydroxyl and carboxyl groups by the ion exchange. |
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